scholarly journals A note about density staircases in the Gulf of Naples : 20 years of persistent weak salt-fingering layers in a coastal area

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Florian Kokoszka ◽  
Daniele Iudicone ◽  
Adriana Zingone ◽  
Vincenzo Saggiomo ◽  
Maurizio Ribera D'Alcalá ◽  
...  
Keyword(s):  
Mixed Layer Depth ◽  
Density Ratio ◽  
Eddy Diffusivity ◽  
Tyrrhenian Sea ◽  
Biological Communities ◽  
Gulf Of Naples ◽  
Critical Range ◽  
Decadal Modulation ◽  
Deep Layers ◽  
Salt Fingering

This is a short communication about the inter-annual recurring presence at the coastal site in the Gulf of Naples of density staircases visible below the mixed surface layer of the water-column, from the end of summer to the beginning of winter, each year during nearly two decades of survey (2001 to 2020). We repetitively observe sequences from 1 to 4 small vertical staircases structures (~ 3 m thick) in the density profiles (~ Δ0.2 kg.m-3), located between 10 m to 50 m deep below the seasonal mixed layer depth. We interpret these vertical structures as the result of double diffusive processes that could host salt-fingering regime (SF) due to warm salty water parcels overlying on relatively fresher and colder layers. This common feature of the Mediterranean basin (i.e., the thermohaline staircases of the Tyrrhenian sea) may sign here for the lateral intrusions of nearshore water masses. These stably stratified layers are characterized by density ratio Rρ 5.0 to 10.0, slightly higher than the critical range (1.0 - 3.0) generally expected for fully developed salt-fingers. SF mixing, such as parameterized (Zhang et al., 1998), appears to inhibit weakly the effective eddy diffusivity with negative averaged value (~ - 1e-8 m2.s-1). A quasi 5-year cycle is visible in the inter-annual variability of the eddy diffusivity associated to SF, suggesting a decadal modulation of the parameters regulating the SF regime. Even contributing weakly to the turbulent mixing of the area, we hypothesis that SF could influence the seasonal stratification by intensifying the density of deep layers. Downward transfer of salt could have an impact on the nutrient supply for the biological communities, that remains to be determined.

scholarly journals A new approach to assess marine opportunity costs and monetary values for spatial planning and conservation; the case study of Gulf of Naples, Mediterranean Sea, Italy

2018 ◽  
Author(s):  
Luca Appolloni
Keyword(s):  
Local Population ◽  
Small Scale ◽  
Conservation Priorities ◽  
Opportunity Costs ◽  
Tyrrhenian Sea ◽  
Economic Activities ◽  
Fishing Activity ◽  
Flexible Approach ◽  
Gulf Of Naples ◽  
Total Turnover

Conservation actions (as Marine Protected Areas) are key tools to maintain coastal ecosystems. However, many reserves are characterized by several problems related to inadequate zonings that preclude important areas from economic activities, determining a strong hostility by local populations. Thus, estimations of marine economic values-in-use are needed for protection of marine ecosystem in order to find the best compromise between conservation priorities and local population needs. Algorithms to estimate monetary values of the main human activities in marine territories (large scale and small scale fishings, aquaculture, beach resorts, yachting, diving and commercial shipping) are here implemented using Gulf of Naples (centre Tyrrhenian sea, Italy) as study area example. These algorithms are based on different sources data (questionnaires, monitoring activities, official local authority reports, web and scientific literature). They can also be compared with each other being their outputs all expressed in the same measure unit. During the models development process a new flexible approach, called “Systematic Costs Assessment” (SCA), to assess opportunity costs in systematic conservation planning process was developed and applied. Results show that the total turnover in the Gulf of Naples is 3,950,753,487 € per year and 747,647,887 € per year excluding small scale fishing estimation, and one hectare of marine territory is worth 40,672 € and 7,696 € per year excluding small scale fishing activity. In particular, excluding small scale fishing activity, beach resort and yachting show the highest values referred to one hectare of marine territories. In conclusion, SCA is a flexible approach where no long and costly sampling campaigns are always needed, provided that two assumptions have to be taken into account, in order to estimate credible values-in-use costs: i) do not use economic activities data and ecosystem services data in the same assessment layer, since it could lead to costs overestimation and ii) SCA method are efficient when used by operators with strong knowledge of the study area, since they are able to recognize parameters affecting economic activities of local population.

scholarly journals Observations of the Transition Layer

2009 ◽  
Vol 39 (3) ◽  
pp. 780-797 ◽  
Author(s):  
T. M. Shaun Johnston ◽  
Daniel L. Rudnick
Keyword(s):  
Layer Thickness ◽  
Mixed Layer ◽  
Potential Vorticity ◽  
Transition Layer ◽  
Mixed Layer Depth ◽  
Density Ratio ◽  
Horizontal Resolution ◽  
Surface Mixed Layer ◽  
Layer Depth ◽  
Vertical Displacements

Abstract The transition layer is the poorly understood interface between the stratified, weakly turbulent interior and the strongly turbulent surface mixed layer. The transition layer displays elevated thermohaline variance compared to the interior and maxima in current shear, vertical stratification, and potential vorticity. A database of 91 916 km or 25 426 vertical profiles of temperature and salinity from SeaSoar, a towed vehicle, is used to define the transition layer thickness. Acoustic Doppler current measurements are also used, when available. Statistics of the transition layer thickness are compared for 232 straight SeaSoar sections, which range in length from 65 to 1129 km with typical horizontal resolution of ∼4 km and vertical resolution of 8 m. Transition layer thicknesses are calculated in three groups from 1) vertical displacements of the mixed layer base and of interior isopycnals into the mixed layer; 2) the depths below the mixed layer depth of peaks in shear, stratification, and potential vorticity and their widths; and 3) the depths below or above the mixed layer depth of extrema in thermohaline variance, density ratio, and isopycnal slope. From each SeaSoar section, the authors compile either a single value or a median value for each of the above measures. Each definition yields a median transition layer thickness from 8 to 24 m below the mixed layer depth. The only exception is the median depth of the maximum isopycnal slope, which is 37 m above the mixed layer base, but its mode is 15–25 m above the mixed layer base. Although the depths of the stratification, shear, and potential vorticity peaks below the mixed layer are not correlated with the mixed layer depth, the widths of the shear and potential vorticity peaks are. Transition layer thicknesses from displacements and the full width at half maximum of the shear and potential vorticity peak give transition layer thicknesses from 0.11× to 0.22× the mean depth of the mixed layer. From individual profiles, the depth of the shear peak below the stratification peak has a median value of 6 m, which shows that momentum fluxes penetrate farther than buoyancy fluxes. A typical horizontal scale of 5–10 km for the transition layer comes from the product of the isopycnal slope and a transition layer thickness suggesting the importance of submesoscale processes in forming the transition layer. Two possible parameterizations for transition layer thickness are 1) a constant of 11–24 m below the mixed layer depth as found for the shear, stratification, potential vorticity, and thermohaline variance maxima and the density ratio extrema; and 2) a linear function of mixed layer depth as found for isopycnal displacements and the widths of the shear and potential vorticity peaks.

Mixing in a Moderately Sheared Salt-Fingering Layer

2011 ◽  
Vol 41 (7) ◽  
pp. 1364-1384 ◽  
Author(s):  
W. D. Smyth ◽  
S. Kimura
Keyword(s):  
Turbulent Mixing ◽  
Linear Growth ◽  
Density Ratio ◽  
Effective Diffusivity ◽  
Shear Instability ◽  
Bulk Richardson Number ◽  
Additional Energy ◽  
Salt Fingers ◽  
Salt Fingering ◽  
Secondary Instabilities

Abstract Mixing due to sheared salt fingers is studied by means of direct numerical simulations (DNS) of a double-diffusively unstable shear layer. The focus is on the “moderate shear” case, where shear is strong enough to produce Kelvin–Helmholtz (KH) instability but not strong enough to produce the subharmonic pairing instability. This flow supports both KH and salt-sheet instabilities, and the objective is to see how the two mechanisms work together to flux heat, salt, and momentum across the layer. For observed values of the bulk Richardson number Ri and the density ratio Rρ, the linear growth rates of KH and salt-sheet instabilities are similar. These mechanisms, as well as their associated secondary instabilities, lead the flow to a fully turbulent state. Depending on the values of Ri and Rρ, the resulting turbulence may be driven mainly by shear or mainly by salt fingering. Turbulent mixing causes the profiles of temperature, salinity, and velocity to spread; however, in salt-sheet-dominated cases, the net density (or buoyancy) layer thins over time. This could be a factor in the maintenance of the staircase and is also an argument in favor of an eventual role for Holmboe instability. Fluxes are scaled using both laboratory scalings for a thin layer and an effective diffusivity. Fluxes are generally stronger in salt-sheet-dominated cases. Shear instability disrupts salt-sheet fluxes while adding little flux of its own. Shear therefore reduces mixing, despite providing an additional energy source. The dissipation ratio Γ is near 0.2 for shear-dominated cases but is much larger when salt sheets are dominant, supporting the use of Γ in the diagnosis of observed mixing phenomena. The profiler approximation Γz, however, appears to significantly overestimate the true dissipation ratio.

scholarly journals Results of the first Wave Glider experiment in the southern Tyrrhenian Sea

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Giuseppe Aulicino ◽  
Yuri Cotroneo ◽  
Teodosio Lacava ◽  
Giancanio Sileo ◽  
Giannetta Fusco ◽  
...  
Keyword(s):  
Optical Properties ◽  
Autonomous Vehicle ◽  
Sea Surface ◽  
Preliminary Evaluation ◽  
Tyrrhenian Sea ◽  
Surface Parameters ◽  
Spatial And Temporal Scales ◽  
Gulf Of Naples ◽  
Southern Tyrrhenian Sea ◽  
Wave Glider

<p>A wave-propelled autonomous vehicle (Wave Glider) instrumented with a variety of oceanographic and meteorological sensors was launched from Gulf of Naples on the 12<sup>th </sup>of September 2012 for a two-week mission in the Southern Tyrrhenian Sea. The main objective of the mission was a preliminary evaluation of the potential of commercial autonomous platforms to provide reliable measurements of sea surface parameters which can complement existing satellite based products moving from the local to the synoptic scale. To this aim Wave Glider measurements were compared to equivalent, or near-equivalent, satellite products achieved from MODIS (Moderate Resolution Imaging Spectroradiometer) sensors onboard the EOS (Earth Observing System) satellite platforms and from AVISO (Archiving Validation and Interpretation of Satellite Oceanographic Data). Level-3 near real time and Level-4 reprocessed sea surface foundation temperature products provided by the CMEMS (Copernicus Marine Environment Monitoring Service) were also included in this study as well as high resolution model output supplied by NEMO (Nucleus for European Modelling of the Ocean). The Wave Glider was equipped with sensors to measure temperature, salinity, currents, as well as Colored Dissolved Organic Matter (CDOM), turbidity and refined fuels fluorescence. The achieved results confirmed the emerging value of Wave Gliders in the framework of multiplatform monitoring systems of the ocean surface parameters. In particular, they showed that Wave Glider measurements captured the southern Tyrrhenian Sea major surface oceanographic features, including the coast to open sea haline gradient and the presence of a cyclone-anticyclone system in the southeastern sub-region. The Wave Glider also had the capability to monitor upper ocean currents at finer spatial and temporal scales than satellite altimetric observations and model outputs. Nonetheless, results stressed the existence of several limits in the combined use of satellite and Wave Glider observations and the necessity of further analyses concerning the monitoring of the ocean optical properties. In fact, Wave Glider and satellite-based products agree in terms of sea surface temperature and currents patterns, while bio-optical properties turned out to be less well correlated. No significant traces of refined fuels have been detected along the WG track.</p>

Multivariate tools to investigate the occurrence of pollutants in a highly anthropised marine area

2020 ◽  
Author(s):  
francesco paolo buonocunto ◽  
nicola cardellicchio ◽  
antonella di leo ◽  
eliana esposito ◽  
luciana ferraro ◽  
...  
Keyword(s):  
Organic Matter ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Organic Matter Content ◽  
Tyrrhenian Sea ◽  
Deep Dive ◽  
Campania Region ◽  
Gulf Of Naples ◽  
Polycyclic Aromatic ◽  
Sarno River

&lt;p&gt;Environmental monitoring of highly anthropised areas demands for deep survey of different environmental compartments (water, sediment, soil and biota) and determination of numerous bio-geo-chemical parameters, due to the huge impact of natural and anthropogenic organic substances constantly released into these environments. However, the interpretation of the large amount of data is not straightforward task due to their complexity that require a very tricky elaboration especially for the decision making processes. Chemo-metrics tools based on the multivariate statistical data analysis seems to be a powerful tool in addressing such complexity (Mali et al., 2017). In this work they are performed to get insight the occurrence of organic pollutants within a highly populated area such as the Gulf of Naples.&lt;/p&gt;&lt;p&gt;The Gulfs of Naples, located along the Eastern Tyrrhenian Sea, is semi-enclosed by the Ischia-Procida Islands to NW, Campi Flegrei and the Campanian Plain in NE, the Sorrento peninsula in SE, and Capri island in W. The Campania region has one of the highest population densities in Italy. The Gulfs of Naples are the receiving environment for persistent toxic substances from the Campania Plain (Albanese et al., 2010; Arienzo et al., 2017). Montuori and Triassi (2012) reported that the discharges of PAHs from the Sarno River to the Gulf of Naples is approximately 8530 g/d. The main goal of this work is to establish the influence of the Campania Plain on the present sedimentation in the Naples bay continental shelf by evaluating organic matter contribution and pollution. For this purpose, superficial sediment samples collected from 158 sites located offshore the Gulf of Naples between Sarno River and Capri Island, were analyzed for total nitrogen and phosphorus, total organic carbon (TOC), grain size, metals, priority polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbon (TPHs), volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), pesticides and organotin compounds (OTs). The adopted multivariate approach allowed, through a clear spatial representation of score plots, a deep dive into the large dataset generated by the investigation campaign, highlighting the influence of some main factors controlling the contamination pattern, such as organic matter content and depositional environment.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Albanese, S., De Vivo, B., Lima, A., Cicchella, D., Civitillo, D., Cosenza, A., 2010. Geochemical baselines and risk assessment of the Bagnoli brownfield site coastal sea sediments (Naples, Italy). J. Geochem. Explor. 105, 19&amp;#8211;33.&lt;/p&gt;&lt;p&gt;Arienzo, M., Donadio, C., Mangoni, O., Bolinesi, F., Stanislao, C., Trifuoggi, M., Toscanesi, M., Di Natale, G., Ferrara, L., 2017. Characterization and source apportionment of polycyclic aromatic hydrocarbons (pahs) in the sediments of gulf of Pozzuoli (Campania, Italy). Mar. Pollut. Bull. 124, 480&amp;#8211;487.&lt;/p&gt;&lt;p&gt;Mali, M., Dell'Anna, M.M., Notarnicola, M., Damiani, L., Mastrorilli, P., 2017. Combining chemometric tools for assessing hazard sources and factors acting simultaneously in contaminated areas. Case study: &quot;Mar Piccolo&quot; Taranto (South Italy). Chemosphere 184, 784-794.&lt;/p&gt;&lt;p&gt;Montuori, P., Triassi, M., 2012. Polycyclic aromatic hydrocarbons loads into the Mediterranean Sea: estimate of Sarno River inputs. Mar. Pollut. Bull. 64, 512&amp;#8211;520.&lt;/p&gt;

Occurrence and distribution of polycyclic aromatic hydrocarbons in mussels from the gulf of Naples, Tyrrhenian Sea, Italy

2016 ◽  
Vol 104 (1-2) ◽  
pp. 386-390 ◽  
Author(s):  
Raffaelina Mercogliano ◽  
Serena Santonicola ◽  
Alessandra De Felice ◽  
Aniello Anastasio ◽  
Nicoletta Murru ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Tyrrhenian Sea ◽  
Gulf Of Naples ◽  
Polycyclic Aromatic

scholarly journals Mixed Layer Lateral Eddy Fluxes Mediated by Air–Sea Interaction

2011 ◽  
Vol 41 (1) ◽  
pp. 130-144 ◽  
Author(s):  
Emily Shuckburgh ◽  
Guillaume Maze ◽  
David Ferreira ◽  
John Marshall ◽  
Helen Jones ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Effective Diffusivity ◽  
Eddy Diffusivity ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Temperature Fields ◽  
Small Scale ◽  
Eddy Diffusivities

Abstract The modulation of air–sea heat fluxes by geostrophic eddies due to the stirring of temperature at the sea surface is discussed and quantified. It is argued that the damping of eddy temperature variance by such air–sea fluxes enhances the dissipation of surface temperature fields. Depending on the time scale of damping relative to that of the eddying motions, surface eddy diffusivities can be significantly enhanced over interior values. The issues are explored and quantified in a controlled setting by driving a tracer field, a proxy for sea surface temperature, with surface altimetric observations in the Antarctic Circumpolar Current (ACC) of the Southern Ocean. A new, tracer-based diagnostic of eddy diffusivity is introduced, which is related to the Nakamura effective diffusivity. Using this, the mixed layer lateral eddy diffusivities associated with (i) eddy stirring and small-scale mixing and (ii) surface damping by air–sea interaction is quantified. In the ACC, a diffusivity associated with surface damping of a comparable magnitude to that associated with eddy stirring (∼500 m2 s−1) is found. In frontal regions prevalent in the ACC, an augmentation of surface lateral eddy diffusivities of this magnitude is equivalent to an air–sea flux of 100 W m−2 acting over a mixed layer depth of 100 m, a very significant effect. Finally, the implications for other tracer fields such as salinity, dissolved gases, and chlorophyll are discussed. Different tracers are found to have surface eddy diffusivities that differ significantly in magnitude.

scholarly journals An Integrated Reconstruction of the Multiannual Wave Pattern in the Gulf of Naples (South-Eastern Tyrrhenian Sea, Western Mediterranean Sea)

2020 ◽  
Vol 8 (5) ◽  
pp. 372
Author(s):  
Simona Saviano ◽  
Daniela Cianelli ◽  
Enrico Zambianchi ◽  
Fabio Conversano ◽  
Marco Uttieri
Keyword(s):  
Wave Field ◽  
Large Scale ◽  
Acoustic Doppler Current Profiler ◽  
Wave Pattern ◽  
Western Mediterranean ◽  
Ocean Dynamics ◽  
Tyrrhenian Sea ◽  
Gulf Of Naples ◽  
South Eastern ◽  
The Impact

Surface gravity waves retrieved by a network of HF (High Frequency) radars and measured in situ by an ADCP (Acoustic Doppler Current Profiler) current meter connected to an elastic beacon were used to carry out a multiple-year characterization of the wave field of the Gulf of Naples (south-eastern Tyrrhenian Sea, western Mediterranean). The aim of the work was to create a climatology of the study area and to demonstrate the potential of an integrated platform for coastal studies. The patterns recorded by the different instruments were in agreement with the wave climatology of the southern Tyrrhenian Sea as well as with previous scores for the same area. The results presented in this work also highlight seasonal and interannual consistency in the wave patterns for each site. In a wider context, this study demonstrates the potential of HF radars as long-term monitoring tools of the wave field in coastal basins, and supports the development of integrated observatories to address large-scale scientific challenges such as coastal ocean dynamics and the impact of global change on the local dynamics.

scholarly journals The Cost for Biodiversity: Records of Ciliate–Nematode Epibiosis with the Description of Three New Suctorian Species

Diversity ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 224 ◽  
Author(s):  
Elisa Baldrighi ◽  
Igor Dovgal ◽  
Daniela Zeppilli ◽  
Alie Abibulaeva ◽  
Claire Michelet ◽  
...  
Keyword(s):  
French Guiana ◽  
Adriatic Sea ◽  
New Records ◽  
Tyrrhenian Sea ◽  
Marine Systems ◽  
Gulf Of Naples ◽  
Mangrove System ◽  
Pockmark Field ◽  
Three New Species ◽  
The Cost

Epibiosis is a common phenomenon in marine systems. In marine environments, ciliates are among the most common organisms adopting an epibiotic habitus and nematodes have been frequently reported as their basibionts. In the present study, we report several new records of peritrich and suctorian ciliates-nematode association worldwide: from a deep-sea pockmark field in the NW Madagascar margin (Indian Ocean), from a shallow vent area in the Gulf of Naples (Mediterranean, Tyrrhenian Sea), in a MPA area in the Gulf of Trieste (Mediterranean, Adriatic Sea), from a mangrove system in French Guiana (South America, Atlantic Ocean), and from the Maldivian Archipelago. In addition, three new species of Suctorea from the Secca delle Fumose shallow vent area (Gulf of Naples) were described: Loricophrya susannae n. sp., Thecacineta fumosae n. sp. and Acinetopsis lynni n. sp. In the light of these new records and data from the existing literature, we discuss the suctorian–nematode epibiosis relationship as a lever to biodiversity.

scholarly journals Syntopic Cystoseira taxa support different molluscan assemblages in the Gulf of Naples (southern Tyrrhenian Sea)

2019 ◽  
Vol 70 (11) ◽  
pp. 1561 ◽  
Author(s):  
Antonia Chiarore ◽  
Iacopo Bertocci ◽  
Sara Fioretti ◽  
Angela Meccariello ◽  
Giuseppe Saccone ◽  
...  
Keyword(s):  
Benthic Fauna ◽  
Shannon Index ◽  
Tyrrhenian Sea ◽  
Brown Macroalgae ◽  
Gulf Of Naples ◽  
Invertebrate Biodiversity ◽  
Southern Tyrrhenian Sea ◽  
Species Specific ◽  
June July ◽  
Shed Light

Brown macroalgae belonging to the genus Cystoseira (Fucales: Sargassaceae) are canopy-forming organisms the recent decline of which at a basin and local scale has been widely documented, which urgently calls for research to fill knowledge gaps and support new and effective measures for protection. We, hereby, characterised the molluscan assemblages associated with three Cystoseira taxa (C. amentacea, C. compressa and C. crinita) from Ischia Island (Italy, Tyrrhenian Sea), and tested whether different congeneric taxa may syntopically support a different biota. In particular, these assemblages were compared among three Cystoseira species, between two times of sampling (June–July 2015 and June–July 2016), and among six sites in terms of multivariate structure (identity and relative abundances of constituting taxa combined, and presence–absence composition), as well as for synthetic measures of diversity, including the total richness of taxa, the exponential Shannon index and the reciprocal Simpson index. In total, 24736 molluscan individuals were collected, overall belonging to 52 taxa. The majority of the identified species included micrograzers and filter feeders, which is in agreement with similar previous studies. The composition of associated molluscan assemblages, which was mainly represented by juvenile individuals, differed among the three Cystoseira species, suggesting that even congeneric taxa do not support an analogous benthic fauna. The present findings have shed light on the molluscan biota associated with Cystoseira taxa in the Gulf of Naples and strengthened the importance of such habitat-forming macroalgae in structuring the local infralittoral invertebrate biodiversity and as a nursery for species-specific associated molluscs.

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